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RE: I factor & API 650 Appendix E

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Keep in mind that API 650 is used by oil companies that generally build
tanks in remote areas away from the general public.  The owners want to get
the cheapest tank for the money ( no different than anyone)  Most of the
time the importance factor of 1.0 is sufficient.

For new tanks that are to be located in areas that are near the public, this
factor is increased.  I have also seen the increase in the use of retaining
walls as a secondary containment.

The problem becomes greater when we are asked to evaluate an existing tank
that was once miles from the public but now homes or business may be located
near by.  By common sense we now have a greater risk.  Using a higher
importance factor now reduces the capacity of the tank and we must tell the
owner that he must install an overflow nozzle at a lower elevation or build
an expensive secondary containment.

I think that it is your call and not unreasonable to increase the factor.

Ronald A. Hill, P.E.
HILL Consulting Engineering
PO BOX 26525
Birmingham, Alabama 35260 USA
Phone: 205-823-4784
FAX: 205-823-4145
email: ronhill(--nospam--at)
-----Original Message-----
From: Robert M. Hanson [mailto:Bob(--nospam--at)] 
Sent: Monday, January 20, 2003 5:43 PM
To: seaint list
Subject: I factor & API 650 Appendix E


I would like to get an opinion or comment on standard practice in
application of I factor when using API 650 code. I found the paper (1978)
where the method was first presented to API as a proposed practice as an
appendix P to API 650. The paper refers to the I at that time in reference
to the Uniform Building Code which had a I of 1.5 for essential facilities
only. This is a gasoline storage tank. To me being downwind of a leaky tank
is a public health hazard and we should be using a I of 1.25.

Robert M. Hanson, SE
Kappa Engineers
(310) 233-3800 x109

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